Kurt began his basketball career in 1985 at Grapeview Public School in St. Catharines Ontario. Thomas regarded his two years at the school as his formative basketball years, driving a source of competitiveness after an incident in which he scored an "own basket" in a city championship game. Thomas later moved to Dallas, and after graduating from Dallas's Hillcrest High School, he attended Texas Christian University, where he led the NCAA Division I in scoring and rebounding in the 1994–95 season with 28.9 PPG and 14.6 RPG, becoming only the third player in history to accomplish this feat (the other two being Hank Gathers and Xavier McDaniel).
On July 20, 2007, Thomas, along with the Suns' first-round draft choices in 2008 and 2010, was traded by the Suns to the Seattle SuperSonics in exchange for a conditional second-round draft choice and an $8 million trade exception.
On July 26, 2010, the Chicago Bulls announced that they had signed Kurt Thomas. Because of injuries to the Bulls' starting center Joakim Noah and power forward Carlos Boozer, Kurt Thomas saw some significant playing time, including 37 starts. When Noah and Boozer came back, he experienced minimal playing time with Ömer Aşık playing in front of him on the bench. Thomas averaged more than 20 minutes per game during the 2010-11 season along with 4.1 points and 5.8 rebounds.
On December 11, 2011, the Portland Trail Blazers signed Thomas for the shortened 2011-2012 season. Though terms for the deal were not disclosed officially, it was reported to be a two-year contract.